Current technologies involving the condensation of amines with perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) require high-boiling point solvents, such as nitrobenzene, trichlorobenzene, N-methylpyrrolidone, benzyl alcohol, lauryl alcohol, quinoline, and the like (e.g., GB 859,288; and WO 2005/078023), and high temperatures, as high as 150°-250° C. (e.g., U.S. Pat. No. 5,225,307; WO 2005/078023; and GB 859,288), to form the condensation products. To lower the reaction temperature, the reaction may be conducted under pressure using a lower boiling point solvent, such as water, chlorobenzenes, and the like. Also, certain catalysts can be used to lower the reaction temperature.
Commonly used catalysts for the condensation reactions include zinc salts, such as anhydrous zinc chloride, anhydrous zinc acetate, zinc oxide, and the like, and acids, such as sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid, p-toluene sulfonic acid, and the like (see, for example, U.S. Pat. No. 4,587,189; and GB 859,288). When zinc salts are used for the condensation reactions, it is necessary to use a large amount of the zinc salts in order to drive the reaction at a reasonable rate and to attain high yields, for example, above 90%. This typically results in the formation of high amount of insoluble sludge in the reaction mixture. To avoid this, the zinc salts need to be highly diluted with a solvent. The lower the dilutions of zinc salt, the more the formation of insoluble sludge, and the harder the agitation and, therefore, the heat transfer during the process. The high amount of insoluble sludge moreover renders the removal thereof from the reaction vessel difficult.
Other solvents such as aluminum chloride and p-toluene sulfonic acid (e.g., WO 2005/078023) have been used to solve the problem, but yields are low and not satisfactory. In addition, the requirement for high levels of zinc salts also leads to the production of the high amount of hazardous wastes containing heavy metal zinc. Thus, the need exists for an alternative catalyst to resolve these problems encountered in condensation reactions.